Triggers directive in Jenkins - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the effect of this Jenkins pipeline triggers directive?

Consider this Jenkins pipeline snippet:

triggers {
  cron('H 4/4 * * 1-5')
}

What does this trigger configuration do?

Jenkins

triggers {
  cron('H 4/4 * * 1-5')
}

A Schedules the job to run every hour at 4 minutes past, Monday to Friday.

B Schedules the job to run every 4 hours on weekdays.

C Schedules the job to run at 4 AM every day from Monday to Friday.

D Schedules the job to run at 4 AM on the first five days of every month.

💡 Hint

Remember that 'H' is a hash-based random minute, and '4/4' means every 4 hours starting at hour 4.

The cron expression 'H 4/4 * * 1-5' means the job runs at a hashed minute (H), every 4 hours starting at hour 4, on weekdays (1-5). So it runs every 4 hours on Monday to Friday.

🧠 Conceptual

intermediate

Which Jenkins trigger directive starts a build when a GitHub push event occurs?

You want your Jenkins pipeline to start automatically when someone pushes code to GitHub. Which trigger directive should you use?

A githubPush()

B pollSCM { cron('H/5 * * * *') }

C upstream('other-job')

D cron('H 0 * * *')

💡 Hint

Think about triggers that respond to external events rather than time schedules.

The 'githubPush()' trigger listens for GitHub push events and starts the build immediately when code is pushed.

❓ Troubleshoot

advanced

Why does this Jenkins pipeline not trigger as expected?

Given this Jenkins pipeline snippet:

triggers {
  pollSCM('H/15 * * * *')
}

The job does not start automatically even though the repository has new commits. What is the most likely cause?

Jenkins

triggers {
  pollSCM('H/15 * * * *')
}

A pollSCM only schedules polling; it does not guarantee immediate builds on new commits.

B The pollSCM trigger requires a webhook to be configured in the repository.

C The Jenkins user does not have permission to access the repository.

D The cron syntax 'H/15 * * * *' is invalid and causes the trigger to fail.

💡 Hint

Consider how pollSCM works compared to event-driven triggers.

pollSCM schedules Jenkins to check the repository every 15 minutes. It does not trigger builds immediately on commit; if polling misses changes or is delayed, builds may not start instantly.

🔀 Workflow

advanced

How to configure a Jenkins pipeline to trigger after another job completes successfully?

You want your Jenkins pipeline to start only after another job named 'Build-App' finishes successfully. Which triggers directive achieves this?

A triggers { cron('H 2 * * *') }

B triggers { pollSCM('H/10 * * * *') }

C triggers { githubPush() }

D triggers { upstream('Build-App', 'SUCCESS') }

💡 Hint

Look for a trigger that listens to other job completions.

The 'upstream' trigger listens for the completion of another job. Specifying 'SUCCESS' means it triggers only if the upstream job finishes successfully.

✅ Best Practice

expert

What is the best practice for using the triggers directive to avoid unnecessary builds?

Which approach best reduces unnecessary Jenkins builds when using triggers in pipelines?

A Disable all triggers and start builds manually to avoid any unnecessary runs.

B Use cron triggers only and avoid event-based triggers to keep builds predictable.

C Use event-driven triggers like githubPush() combined with minimal polling to reduce load.

D Use pollSCM with a very frequent schedule like every minute to catch all changes quickly.

💡 Hint

Think about balancing responsiveness and resource use.

Event-driven triggers like githubPush() start builds immediately on changes, reducing unnecessary polling. Minimal polling can catch missed events, balancing load and responsiveness.